Keel for an airship



FIG. 1 is a side elevation view of a keel for an airship showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 s a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown in the drawings represent structural environment and form no part of the claim. 

The ornamental design for a keel for an airship, as shown and described. 